The Darkness Civilization
(the following is compiled from information given on the Wizards Of The Coast Official Duel Masters Site from the Creature Profiles of J. Kovach - currently unaltered)

Toxic gas fills the air and total darkness envelops the vast underground world of the Darkness civilization. Here in this inhospitable place, lifespans are short, and inhabitants are consumed with the desire for immortality. Endless attempts to lengthen their lives have served only to spoil the land and contaminate their surroundings.

Experiments have generated numerous deadly diseases, disrupted the space-time continuum, and poisoned and confused the natural order of things. For now, only a few cities remain in a jumble of clashing architecture. Every one and everything is out of sync, life is incoherent and events are incongruous. It is as if a demon had cast a spell on them all.

Darkness creatures are most easily recognized by their masks and armor made of bone. Their bodies are disfigured and misshapen, with flesh rotting off, from the toxic gas and diseases that pervade their world. After living in darkness for so long, most Darkness creatures are completely blind.

To survive the toxic gas, Darkness creatures keep their masks on at all times. Even outside of the Dark world, they are unable to survive without gas masks. Consequently, they are extremely vulnerable in a clean-air environment.

Darkness inhabitants are on a never-ending search for immortality. Driven by madness and selfishness, tormented by fear and despair, they struggle to conquer and control.

Toxic gases and despair permeate everything in the bleakness that is the Darkness Civilization. Deep within the earth lies the filth and disease that the creatures from this banal society live and die in everyday. Death is commonplace, but the weary dead do not rest--these creatures rise again to become nothing more than rotted, animated corpses. Their nature is unerringly territorial and violent. Their desire to destroy anything living comes from the harsh jealousy they feel toward those that live above them in the clean light. It is utter chaos at every moment beneath the earth. These sorry souls struggle against the fiery, acrid elements that rend skin from bone and poison everything in sight. Except, of course, for the Dark Lords. These power-mad nobles walk with confidence and pride above the tumult of the few living and the countless dead. They revel in the suffering of their lessers, and demand staunch obedience and respect at all times. Their cruelty is unmatched. General Dark Fiend himself makes it a habit to cut a swath through the horde of great unwashed with his mighty sword as he strolls to his castle for lunch.

In the cruel, putrid environment that is the Underdark, there exists a way of life almost as poisonous as the very air: the wretched inhabitants seek out ways to cheat and destroy one another in a perverse attempt to discover the secret to eternal life. During the great cataclysm that depleted the once vast underground landscape, many of the creatures suddenly realized just how fragile life was and how easily it could be taken away en masse. It became common belief that the great explosion was a punishment for holding too greedily onto life itself. The quest for immortality became a religion, and sacrifice for that cause became its one and only tenet. For thousands of years, the creatures have conducted grueling, inhuman experiments on one another--both willingly and unwillingly--to achieve eternal life. This has so befouled the entire civilization that none can breathe without a gas mask except for the Ghost race.

The entrance most used to gain access to the underdark by those that live there is called the Black Maze of Tears--this is considered the 'front door' to the realms of Darkness. It is a living maze of tunnels that cross over each other, dead end, and roll back on themselves. Some points of the caves twist down into openings barely large enough for a small human to snake through. Throughout this 300 mile knot of caves are reservoirs of space that are inhabited by groups from the different races of the Dark. These races keep mutated monsters in the reservoirs with them. Any creatures that attempt to gain access to the main living areas of the underdark had better be welcome, or else be prepared for inevitable death in the pitch blackness of the Maze. Further, many of the caves were carved by water, from sources that are still present in the underdark--however, all such water is contaminated by putrid disease. When traveling through the caves, there is no way to avoid contact with this tainted water--it is the one element that will, eventually, cause the demise of any invader.

The only belief the wretched creatures of the Darkness civilization share with each other is that they can achieve eternal life. They have sacrificed what was once a pristine and magical network of caves in the Underdark in order to fulfill this desire. Because of the massive experiments to find eternal life, the sacrifices of thousands to find the soul, and the fetid pools of disease developed to cause life everlasting with a virus, everything in this world is befouled. This driving goal haunts these creatures day and night, an obsession that festers in every individual, living and dead, by the constant experimentation of the Dark Lords. This is an unholy religion to the creatures of the Dark, and many have sacrificed their lives for it.